Sinusoidal oscillators



Dec. 13, 1955 K. N. FROMM SINUSOIDAL OSCILLATORS Original Filed Feb. 28, 1950 Fig.2A.

INVENTQR Kenneth N.Fromm. BY 'I;TTRNEY United States Patent SINUSOIDAL OSCILLATORS Kenneth N. Fromm, Columbus, Ohio, assigns: to West= inghouse Electric Corporation, East Pittsburgh, P2,, a corporation of Pennsylvania Original application February 28, 1950, Seriai No. 146,713. Divided and this application Gctober 26, 1951, Serial No. 253,381

9 Claims. (Cl. 25035) My invention relates to electrical circuits, and more particularly to electrical circuits for producing sinusoidal oscillations.

This application is a division of my copending application, entitled Sinusoidal Oscillators, filed February 28, 1950, Serial No. 146,713, and assigned to the assignee of this application now abandoned.

Apparatus for producing oscillations in accordance with the teaching of the prior art of which I am aware, includes a thermionic tube or tubes, the electrodes of which are interconnected through a feedback loop. Such oscillators are of relatively complex structure. Because of the number of components of these oscillators which may vary as ambient conditions vary or as the component age, is relatively large, they are at times, of doubtful reliability and stability. Moreover, where large numbers of oscillators are used, as for example, in a calculating machine (one such machine includes approximately 15,000 tubes) filament supply presents a serious problem. During operation of a system including a large number of oscillators, the filaments may draw many kilowatts of power and unreasonably load the power supply facilities. This filament power problem is accentuated by the fact that tubes have a longer life if their filaments are maintained heated continuously. In order to economize on the number of tubes used in such service, to the extent practicable, the filaments are heated continuously.

It is an object of my invention to provide an oscillator for producing sinusoidal oscillations which shall perform in a manner superior to present oscillators and shall be compact and simple in structure.

Another object of my invention is to provide an oscillator which shall not require filament power.

An ancillary object of my invention is to provide a circuit for producing sinusoidal oscillations in which there is a single tuned network.

It is another ancillary object of my invention to provide an improved oscillator for producing sinusoidal oscillations which is devoid of tapped coils.

Recent developments in the art of solid conduction have produced a device which can perform some of the functions of a vacuum tube. This device, termed a transistor, comprises a block of semi-conductive material such as silicone or germanium, with which are associated three electrodes. Two of these electrodes, called the emitter and the collector, are conductive probes having relatively small contact areas and are located in proximity to each other on one face of the semi-conductive block. The third electrode, called the base electrode which is a conductor having a relatively large contact area, is placed contiguous to the opposite face of the semi-conductive block.

In accordance with my invention 1 provide a novel oscillator including a transistor. Such an oscillator is of simple and compact structure and is very reliable in operation.

My invention, together with additional objects and advantages thereof, will be best understood from the fol- 2,727,146 Patented Dec. 13, 1955 ice lowing description, taken in connection with the accompanying drawing, in which:

Figure 1 is a schematic diagram showing one embodiment of my invention;

Fig. 1A is a schematic diagram showing a modification of Fig. 1;

Fig. 2 is a schematic diagram showing another embodiment of my invention; and

Fig. 2A is a schematic diagram showing a modification of Fig. 2.

In Fig. 1 there is shown a semi-conductive device which may be a transistor indicated generally at 11. The transistor comprises a block of semi-conducting material 13 which may be silicone or germanium, and with which are associated emitter, collector and base electrodes 15, 17, 19 respectively. The emitter and collector electrodes 15, 17 are pin-pointed conductive probes which are located in proximity to each other on one face of the semi-conducting block 13. The base electrode 19 is a rectangular block of conductive material which is placed contiguous to the opposite face of the semi-conducting block. A tunable network 21 comprising an inductance 23 and capacitance 25 in parallel is connected from the base electrode to a ground at 27. An emitter bias resistance 29 is connected in series with a source of direct current positive bias 31 between the emitter electrode 15 and ground at 27. A collector bias resistance 33 is connected in series with a source of negative direct current bias 35 between the collector electrode 17 and ground at 27. The output of the oscillator may be taken from a connection through a coupling capacitor 37 to the collector electrode 17. A synchronizing signal may be applied through a coupling capacitor 39 which is connected to the emitter electrode 15 if desired.

The circuit just described has been used in actual practice and has been found to have good stability. In this practice the following circuit constants were used and parameters noted: emitter bias resistance 470 ohms, emitter bias voltage 0.15 volt, collector bias resistance 30,000 ohms, collector bias voltage 86 volts, tuned circuit inductance l millihenry, tuned circuit capacitance 0.001 microfarad, emitter current 0.6 milliampere, collector currents 2.1 milliamperes, operating frequency kilocycles.

The circuit shown in Fig. 1A is similar in organization and operation to that shown and described for Fig. 1, except that self-bias is included. The emitter direct current bias supply 31 has been removed and a cathode bias resistance 41 has been inserted between the tunable network 21 and ground at 27. A by-pass capacitor 43 is inserted across this resistance 41. The cathode bias resistance 41 must be adjusted to provide proper bias for oscillation. In practice I have used a 1500 ohm variable resistor for the cathode bias resistance and a value of 1 microfarad for its by-pass capacitance.

In Fig. 2 there is provided a transistor having emitter, collector, and base electrodes 47, 49, 51. This transistor 45 has a negative resistance characteristic (plotting collector voltage vs. collector current for various values of emitter voltage). A capacitance 53 is connected between the emitter and collector electrodes 47, .9. An emitter bias resistance 55 is connected in series with a positive direct current bias supply 57 between the emitter electrode 4-7 and ground at 59. A capacitance 61 is shunted across the emitter bias resistance 55. The base electrode 51 is connected to ground at 59. An inductance 63 in series with a negative direct current bias supply 65 is connected between the collector electrode 49 and ground at 59. This inductance 63 is shunted by a capacitance 67, which may be simply the shunt distributed capacitance of the inductance 63 and the external circuit. The output of the oscillator may be taken from a connection to 3 the collector electrode 49. A synchronous signal may be applied to the emitter electrode 47 if desired.

This circuit is well suited for applications in receivers as local oscillators where better than usual stability is desired. The frequency of this oscillator is practically independent of the collector bias voltage. This oscillator has been operated at a frequency range from 100 cycles per second to 4 megacycles per second. In this operation, the following circuit constants were used: emitter bias resistance 47 ohms, emitter bias voltage 0.8 volt, emitter bias resistor by-pass capacitor 0.01 microfarad, collector circuit inductance l0 microhenries, collector bias supply 85 volts, emitter collector coupling capacitance 0.0001 microfarad, collector circuit inductance by-pass capacitance was the distributed capacitance of the collector circuit inductance.

The circuit of Fig. 2A is identical in organization and operation to that or Fig. 2 except that self-bias is provided. The emitter direct current bias supply 57 has been eliminated and a cathode resistance 69 has been inserted between the base electrode 51 and ground at 59. This resistance is shunted by a capacitance 71. In practice I have used values of 1500 ohms and 1 microfarad respectively for these components.

The theory of operation of the semi-conductive devices which are used in the circuits disclosed is not at present well understood. Insofar as I am aware, the art relating to such semi-conductive devices has not yet been developed to a point where their characteristics of operation are scientifically predictable. As a consequence I am unable to give an explanation for the operation of the circuits disclosed. However, i have put them into actual practice and have found that they operate satisfactorily.

The circuits of the oscillators of my invention are very much simpler than corresponding vacuum tube circuits. in these oscillators only one tuned circuit and no tapped coils are used.

I am aware that some modifications of the specific circuits disclosed may be made without departing from the scope of my invention. I desire, therefore, to be limited only insofar as is necessitated by the prior art and the spirit of the appended claims.

I claim as my invention:

1. An oscillator circuit, including a semi-conductive device having emitter, collector, and base electrodes and having a negative resistance characteristic, means for supplying positive bias potential connected between said emitter electrode and a common point, means for supplying negative bias, a tunable network, said last-named means and said tunable network being connected between said collector electrode and said common point, and a direct connection from said base electrode to said comrnon point.

2. An oscillator circuit, including a semi-conductive device having emitter, collector, and base electrodes and having a negative resistance characteristic, a capacitance connected between said emitter and collector electrodes, means for supplying positive bias potential connected between said emitter electrode and a common point, means for supplying negative bias, a tunable network, said lastnarned means and said tunable network being connected between said collector electrode and said common point, and a direct connection from said base electrode to said common point.

3. An oscillator circuit, including a semi-conductive device having emitter, collector, and base electrodes and having a negative resistance characteristic, means for supplying positive bias potential connected between said emitter electrode and a common point, means for supplying negative bias, a tunable L.-C. network, said lastnamed means and said tunable network being connected between said collector electrode and said common point, and a direct connection from said base electrode to said common point.

4. An oscillator circuit, including a semi-conductive device having emitter, collector, and base electrodes and having a negative resistance characteristic, a capacitance connected between said emitter and collector electrodes, means for supplying positive bias potential connected between said emitter electrode and a common point, means for supplying negative bias, a tunable L.-C. network, said last-named means and said tunable network being connected between said collector electrode and said common point, and a connection from said base electrode to said common point.

5. A sinusoidal oscillator circuit, including a semi-com ductive device having emitter, collector and base electrodes and having a negative resistance characteristic, a capacitance connected between said emitter and collector electrodes, means including a potential source and a resistance connected in series between said emitter and base electrodes for obtaining a positive bias on said emitter electrode, a ca acitance in shunt with said resistance, a-

source negative potential, and a tunable L.-C. network connected in series between said collector and base electrodes.

6. A sinusoidal oscillator circuit, including a semi-conductive device having emitter, collector, and base electrodes and having a negative resistance characteristic, a capacitance connected between said emitter and collector electrodes, means for obtaining self-bias for said emitter electrode, a source of negative potential, a tunable network, said potential source and said network being connected in series between said base and collector electrodes.

7. An oscillator circuit, including a semi-conductive device having emitter, collector, and base electrodes, and having negative resistance characteristic, a capacitance connected between said emitter and collector electrodes, a resistance and a capacitance connected in parallel between said base electrode and a common point, a tunable L-G circuit connected in series with a source of negative potential between said collector electrode and said common point, and a resistance connected between said emitter electrode and said common point.

8. An oscillator circuit, including a semi-conductive device having emitter, collector, and base electrodes, and having a negative resistance characteristic, a capacitance connected between said emitter and collector electrodes, a resistance and a capacitance connected in parallel between said base electrode and a common point, a tunable L.-C. circuit connected in series with a source of negative potential between said collector electrode and said common point, and a resistance shunted by a capacitance connected between said emitter electrode and said common point.

9. An oscillator circuit, including a semi-conductive device having emitter, collector, and base electrodes, a

capacitance connected between said emitter and collector electrodes, means for supplying bias potential to said emitter and collector electrodes, a tunable L.-C. circuit connected in series with said collector electrode and said base electrode, and a resistor shunted by a capacitance connected in series with said emitter electrode and said Article in Radio Craft for September, 1948 entitled Eclipse of the Radio Tube, pages 24 and 25. 

